Biodegradation of mononucleotides to nucleosides and free bases

An intracellular phosphate, non repressible alkaline phosphate found in extracts of Penicillium brevicompactum NRC829 could catalyze dephosphorylation of ribonucleotides AMP, GMP, CMP, UMP and phenyl disodium orthophosphate (phph) optimally at pH 9.0 and 60 degrees C. The extracts contain also hydrolytic deamination activities with adenosine, cytidine and cytosine out of the tested ribonucleotides, ribonucleosides and bases. While the optimum activity of deamination of adenosine or cytidine was achieved at pH 7.0 and 50 degrees C. Neither cleavage of the N-glycosidic linkages of these nucleotides nor those of the corresponding nucleosides could be affected by the extracts. Heating the extracts at 80 degrees C for 10 min, in absence of the substrate, inactivated the two enzymes. The extracts catalyzed hydrolytic cleavage of phosphate esters of different phosphorylated compounds with different rates. Hence, the enzyme appears to have abroad substrate specificity and the highest relative rate of hydrolysis was with UMP. No evidence for the involvement of specific nucleotidases in ribonucleotide dephosphorylation was recorded.